Wide bandgap (WBG) power devices such as SiC and GaN power devices can provide superior performance characteristics relative to Si power devices for many high power applications. For example, as disclosed in an article by J. Burm et al., entitled “Wide Band-Gap FETs for High Power Amplifiers,” Journal of Semiconductor Technology and Science, Vol. 6, No. 3, pp. 175-182, September 2006, wide bandgap semiconductor materials having band-gap energy levels in a range from about 2 eV to about 6 eV may be utilized to provide high breakdown voltages for high power generation in power amplifiers and low dielectric constants for better isolation and lower coupling. Similarly, as disclosed in an article by J. Reed et al., entitled “Modeling Power Semiconductor Losses in HEV Powertrains using Si and SiC Devices,” Vehicle Power and Propulsion Conference (VPPC), 2010 IEEE, September 1-3 (2010), silicon carbide (SiC) power devices can have potential benefits over conventional silicon-based devices, particularly in high power electronic converters.
Examples of high power switches that embody wide bandgap semiconductors are disclosed in U.S. Pat. Nos. 7,556,994 and 7,820,511 to Sankin et al., which illustrate normally-off vertical JFET integrated power switches, U.S. Pat. No. 7,230,273 to Kitabatake et al., which describes a plurality of wide bandgap switching elements connected in parallel to increase device yield, and U.S. Pat. No. 8,017,978 to Lidow et al., which illustrates multiple power devices of different type connected in series. These SiC and other wide bandgap power devices can provide greater power converter efficiency and power density by operating at higher switching frequencies and temperatures. However, all-SiC high-power converters with exclusively SiC devices will significantly increase the semiconductor device cost, especially if the power converters need to meet any overload requirements and the semiconductor devices are sized according to overload requirements. For example, in Uninterruptable Power Supply (UPS) applications, typically the overload performances are 150% overload for 10 s to 60 s and 200% overload for 10 to 20 cycles (with the current limit).
To address this excessive cost issue and meet overload requirements, higher and lower cost devices may be paralleled together as a hybrid device, which may be capable of more fully utilizing each of the individual devices positive characteristics so that a higher power rating may be achieved at lower overall cost. Examples of such hybrid devices are disclosed in articles by Jih-Sheng Lai et al., entitled “A Hybrid-Switch-Based Soft-Switching Inverter for Ultrahigh-Efficiency Traction Motor Drives,” IEEE Transactions on Industry Applications, Vol. 50, No. 3, May/June (2014); and Pengwei Sun, et al., entitled “A 55-kW Three-Phase Inverter Based on Hybrid-Switch Soft-Switching Modules for High-Temperature Hybrid Electric Vehicle Drive Application,” IEEE Transactions on Industry Applications, Vol. 48, No. 3, May/June (2012). Still further hybrid power devices are disclosed in commonly assigned U.S. Publ. App. No. 2014/0185346, entitled “Hybrid Power Devices and Switching Circuits for High Power Load Sourcing Applications,” the disclosure of which is hereby incorporated herein by reference. Notwithstanding these devices, there continues to be a need for more efficient methods of operating hybrid power devices for higher performance and efficiency and lower overall cost.